1. Technical Field
The disclosure relates to a screw fastening method and a screw fastening device.
2. Description of Related Art
When fastening an external thread and an internal thread, screwing may begin in such a state whereby a rotation axis of one of the threads is tilted with respect to a rotation axis of the other thread, thereby causing the external thread and the internal thread to become jammed.
In order to address this, in a screw fastening method disclosed in Japanese Patent Application Publication No. 2006-315097 (JP 2006-315097 A), either an external thread in a non-screwed state or an internal thread in a non-screwed state, which is engaged with a shaft part of a fastening tool, presses the other thread, and, while doing so, the shaft part is rotated reversely in a thread loosening direction. In this state, vibrations caused by collisions between the external thread and the internal thread are detected. By doing so, a starting position of screwing is detected, at which the external thread and the internal thread are prevented from becoming jammed. Thread ridges of the external thread and the internal thread collide with each other every time the shaft part makes one reverse rotation.